Business Analytics

Pre-requisite

Before we begin

Please install and load the following packages

library(dplyr)
library(tidyverse)
library(scales)
library(patchwork)
library(ggiraph)
library(gghighlight)

Access lecture slide from the course landing page

About me

Learning Objectives

Let’s Recap

• In the data visualization lecture, you learnt how to create various types of graphs using ggplot2
• Some of them include bar, graph, line graph, scatter plots etc
• For effective data visualization and communication, any plot requires modifications
• These include annotations on the plot, modification of axes and scales, highlighting and interactivity of the plot
• The aim of this lecture is to move beyond making graphs, towards clear and effective visualizations

Annotations in ggplot - Text

Content for this topic has been sourced from ggplot2. Please check out the work for detailed information.

• In addition to plotting your graph, you want to provide additional details to explain your graph
• Text annotations are useful in this case
• The annotate() function can be used for any kind of geometric object
• In the annotate() function, the type of geom is specified first
• Then, the positining is required (x and y coordinates in this case)
• This is followed by the label

ggplot(mtcars, aes(x = wt, y = mpg)) +
   geom_point()+
   annotate("text", x = 4, y = 25, label = "Annotation Text")

Annotations in ggplot

Content for this topic has been sourced from ggplot2. Please check out the work for detailed information.

• Further, annotations can be customized

 ggplot(mtcars, aes(x = wt, y = mpg)) +
   geom_point()+
   annotate("text", x = 4, y = 25, label = "Annotation Text", colour = "orange", size = 8)

 ggplot(mtcars, aes(x = wt, y = mpg)) +
   geom_point()+
   annotate("text", x = 1:5, y = 6, label = "Annotation Text", colour = "orange", size = 3)

Annotations in ggplot

Content for this topic has been sourced from ggplot2. Please check out the work for detailed information.

• Similar to text annotation, other geoms can be used for annotations
• However, instead of x and y, xmin and xmax is used for coordinates of the rectangle
• Do you remember what alpha is used for?

ggplot(mtcars, aes(x = wt, y = mpg)) +
   geom_point()+
   annotate("rect", xmin = 4.8, 
            xmax = 5.7,
            ymin = 10,
            ymax = 18.6, 
            alpha = .2)

Annotations in ggplot

Content for this topic has been sourced from ggplot2. Please check out the work for detailed information.

• Suppose you want to add a line segment to your graph
• annotate() over here requires x and xend coordinates

ggplot(mtcars, aes(x = wt, y = mpg)) +
   geom_point()+
   annotate("segment", x = 4.8,
            xend = 5.7,
            y = 10,
            yend = 18.6,
            colour = "red")

Do it Yourself -1

Scales Functions in ggplot2 - Why?

• When you create a graph, using ggplot2, the axes are mapped automatically based on the data
• However, you would often need to change the axes in order to effectively present the data
• the scale functions in ggplot2:
  • control how the data is plotted
  • allow manipulation of axes
  • improves overall appearances of the plot for effective data communication

Scales Functions in ggplot2

• Look at the scatter plot of wt and mpg

ggplot(mtcars, aes(x = wt, y = mpg)) +
   geom_point()

• What if you want both the axes to start from 0?
• scale_y_continuous() allows you to set the range for the y-axis
• limits inside the scale_y_continuous() provides limits of the scale
• Over here, NA is used to refer to the existing maximum

ggplot(mtcars, aes(x = wt, y = mpg)) +
   geom_point()+
  scale_y_continuous(limits = c(0, NA))

Scales Functions in ggplot2

• Instead of using NA, if you had to provide 40 as the limit for y-axis

ggplot(mtcars, aes(x = wt, y = mpg)) +
   geom_point()+
  scale_y_continuous(limits = c(0, 40))

Scales Functions in ggplot2 - Adding breaks

• Setting breaks in the scale_y_continuous allows you to set what intervals the axis will have

ggplot(mtcars, aes(x = wt, y = mpg)) +
   geom_point()+
  scale_y_continuous(breaks = seq(0, 40, 7))

Scales Functions in ggplot2

Content for this topic has been sourced from ggplot2. Please check out the work for detailed information.

• The scale_colour_brewer() options are useful for plotting discrete values on your graph
• The brewer scales provide sequential colour schemes from ColorBrewer
• Look at the two charts
• scale_colour_brewer helps in effcient mapping of discrete variables

ggplot(mpg, aes(x = displ, y = cty)) +
   geom_point(aes(colour = class))

ggplot(mpg, aes(x = displ, y = cty)) +
   geom_point(aes(colour = class))+
  scale_colour_brewer()

Do It Yourself -2

Scales Package